The discovery of a young, energetic X-ray pulsar associated with HESS J1640-465 provided important new constraints on possible emission models for this Galactic TeV source, the most luminous known. The 206 ms pulsar PSR J1640-4631 and its surrounding PWN lie within SNR G338.3-0.0 and are co-located with the gamma-ray source HESS J1640-465 and possibly 1FHL J1640.5-4634.
The NuSTAR discovery and subseqüent spin-down measurements imply Edot = 4.4E36 erg/s, Bs = 1.4E13 G, tau = 3350 yrs. The origin of the gamma-ray emission is difficult to discern given the complex local environment, both leptonic and hadronic models have been proposed. We present an evolutionary SNR/PWN model fit to the spectral energy distribution of HESS J1640-465 using updated spectral data and input parameters. The pulsar energetics predict an initial spin period < 15 ms and a braking index less than or equal to. 2. A NuSTAR program to measure the pulsar's braking index is underway
to better constrain its true age.